Cross-linking Structure and Rheology Properties of Hydrogels Produced by UV Irradiation to Aqueous Solutions of Poly(sodium acrylate)

Abstract

Hydrogels were prepared by UV irradiation to aqueous solutions of poly(sodium acrylate) with different polymerization degrees in the presence of a radical initiator. When potassium persulfate or ammonium persulfate was used as an initiator, gels were efficiently produced. The effects of the polymerization degree and the concentration of the polymer, the type and concentration of the initiators, and the UV irradiation time on the gel fraction and the swelling ratio of the produced gel were clarified. The storage modulus (G'), loss modulus (G"), and complex viscosity (|η*|) of the isolated gels were determined by rheological measurement. The relation of the swelling ratio and cross-linking density of the gels and the rheological properties as well as the radical reaction mechanism for gel formation were discussed. Furthermore, hydrogels with a cross-linked structure inclined in the depth direction were synthesized by controlling the absorption energy of irradiated UV light.